Simplify the following expression: $5\sqrt{80}$.
First, try to factor a perfect square out of the radical. $= 5\sqrt{80}$ $= 5\sqrt{16 \cdot 5}$ Separate the radical and simplify. $= 5\sqrt{16} \cdot \sqrt{5}$ $= 5 \cdot 4 \cdot \sqrt{5}$ $= 20\sqrt{5}$